Nanomia Siphonophore      Nanomia bijuga



WOW,talk about a weird animal!  This relative of jellyfish was an surprise visitor to the Boston Harbor Marina during a night lighting event.  Nanomia, with a body length of only an inch or so (tentacles can expand to 12 inches), is one of many types of siphonophores that include such well known species as Portuguese man-of-war (Physalia) and the sail jellyfish or by-the-wind-sailor (Velella). Siphonophores are mainly deep water, open ocean creatures, many of which have only recently been identified by the use of unmanned underwater cameras.


Lets take a tour of Nanomia's anatomy: At the top left is a large red-tipped, gas-filled buoyancy device called a pneumatophore.  Connected to it and extending to the right is a straight, chain-like set of swimming bells or nectophores (slightly out of focus) that move the animal . Hanging down from the end of the nectophore segment are retractable tentacles that are used to catch prey. The red tips on the tentacles are thought to mimic small crustaceans and so act as lures. Mixed in with the tentacles are groups of colorless reproductive structures.


But the most fascinating fact about this animal, and all siphonophores, is that it is not a single animal at all, but a colony of specialized creatures each contributing to the common welfare.


This species is quite common in nearshore waters to a depth of around a thousand feet although it occasionally appears at the surface.  It ranges throughout the temperate and tropical portions of the Atlantic, Pacific and Indian Oceans. Recent remote camera work has shown that this species is a major source of the deep scattering layer as seen on boat depth sounders because the swimming bells are of the proper size to reflect the sound frequencies used in sonar.


Thanks to Gabrielle Byrne of People for Puget Sound for help in identification.